Behavior of [2.n]metacyclophanes-fused cyclobutane ring in bromination

Dimethoxy[2.2]metacyclophane mainly gave a tetrahydropyrene structure and the other [2.n]metacyclophane derivatives (n=3–5) gave aromatic bromides like pseudo-ipso and/or pseudo-ortho dibromides in the reaction with bromine. They also gave benzyl bromides by cyclobutane ring-opening.